import 'dart:convert';
import 'dart:math';

import 'package:flutter/foundation.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../engine/stroke_geometry.dart' show kDefaultPenThinning;

/// Action that can be triggered by a hardware pen button or the eraser end.
enum PenButtonAction {
  none,
  eraser,
  undo,
  toggleTool,
  pan,
}

/// Immutable configuration for pen input behaviour.
///
/// Persisted under SharedPreferences key [PenConfigController.prefsKey].
class PenConfig {
  const PenConfig({
    this.sideButton = PenButtonAction.eraser,
    this.eraserEnd = PenButtonAction.eraser,
    this.pressureGamma = 1.0,
    this.palmRejectionMs = 150.0,
    this.fingerDrawing = false,
    this.penWidth = 0.004,
    this.highlighterWidth = 0.02,
    this.pressureSensitivity = kDefaultPenThinning,
  })  : assert(pressureGamma >= 0.3 && pressureGamma <= 3.0,
            'pressureGamma must be in [0.3, 3.0]'),
        assert(palmRejectionMs >= 0.0 && palmRejectionMs <= 500.0,
            'palmRejectionMs must be in [0, 500]'),
        assert(pressureSensitivity >= 0.0 && pressureSensitivity <= 1.0,
            'pressureSensitivity must be in [0, 1]');

  /// Which action fires when the side barrel button is held.
  final PenButtonAction sideButton;

  /// Which action fires when the eraser end of the pen is used.
  final PenButtonAction eraserEnd;

  /// Gamma exponent for the pressure curve: effective = pressure ^ gamma.
  /// Range: [0.3, 3.0], default 1.0 (linear).
  final double pressureGamma;

  /// Duration in milliseconds after a pen-down event during which touch
  /// contact is treated as palm and rejected.
  /// Range: [0, 500], default 150.
  final double palmRejectionMs;

  /// Whether finger touch strokes are drawn when no pen is present.
  final bool fingerDrawing;

  /// Pen stroke width as a fraction of the canvas width.
  final double penWidth;

  /// Highlighter stroke width as a fraction of the canvas width.
  final double highlighterWidth;

  /// How strongly stylus pressure modulates stroke width — maps directly to
  /// perfect_freehand's `thinning`. Range [0,1]; `0` = constant width,
  /// higher = pressure sweeps width more (Saber's `StrokeOptions.thinning`
  /// model). Default [kDefaultPenThinning] so the out-of-box feel and the
  /// export golden are unchanged.
  final double pressureSensitivity;

  PenConfig copyWith({
    PenButtonAction? sideButton,
    PenButtonAction? eraserEnd,
    double? pressureGamma,
    double? palmRejectionMs,
    bool? fingerDrawing,
    double? penWidth,
    double? highlighterWidth,
    double? pressureSensitivity,
  }) {
    return PenConfig(
      sideButton: sideButton ?? this.sideButton,
      eraserEnd: eraserEnd ?? this.eraserEnd,
      pressureGamma: pressureGamma ?? this.pressureGamma,
      palmRejectionMs: palmRejectionMs ?? this.palmRejectionMs,
      fingerDrawing: fingerDrawing ?? this.fingerDrawing,
      penWidth: penWidth ?? this.penWidth,
      highlighterWidth: highlighterWidth ?? this.highlighterWidth,
      pressureSensitivity: pressureSensitivity ?? this.pressureSensitivity,
    );
  }

  Map<String, dynamic> toJson() => {
        'sideButton': sideButton.name,
        'eraserEnd': eraserEnd.name,
        'pressureGamma': pressureGamma,
        'palmRejectionMs': palmRejectionMs,
        'fingerDrawing': fingerDrawing,
        'penWidth': penWidth,
        'highlighterWidth': highlighterWidth,
        'pressureSensitivity': pressureSensitivity,
      };

  factory PenConfig.fromJson(Map<String, dynamic> json) {
    return PenConfig(
      sideButton:
          PenButtonAction.values.asNameMap()[json['sideButton'] as String? ?? ''] ??
              PenButtonAction.eraser,
      eraserEnd:
          PenButtonAction.values.asNameMap()[json['eraserEnd'] as String? ?? ''] ??
              PenButtonAction.eraser,
      pressureGamma: (json['pressureGamma'] as num?)?.toDouble() ?? 1.0,
      palmRejectionMs: (json['palmRejectionMs'] as num?)?.toDouble() ?? 150.0,
      fingerDrawing: json['fingerDrawing'] as bool? ?? false,
      penWidth: (json['penWidth'] as num?)?.toDouble() ?? 0.004,
      highlighterWidth: (json['highlighterWidth'] as num?)?.toDouble() ?? 0.02,
      pressureSensitivity:
          (json['pressureSensitivity'] as num?)?.toDouble() ?? kDefaultPenThinning,
    );
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is PenConfig &&
          runtimeType == other.runtimeType &&
          sideButton == other.sideButton &&
          eraserEnd == other.eraserEnd &&
          pressureGamma == other.pressureGamma &&
          palmRejectionMs == other.palmRejectionMs &&
          fingerDrawing == other.fingerDrawing &&
          penWidth == other.penWidth &&
          highlighterWidth == other.highlighterWidth &&
          pressureSensitivity == other.pressureSensitivity;

  @override
  int get hashCode => Object.hash(
        sideButton,
        eraserEnd,
        pressureGamma,
        palmRejectionMs,
        fingerDrawing,
        penWidth,
        highlighterWidth,
        pressureSensitivity,
      );
}

/// Applies a gamma power curve to a raw pressure value.
///
/// Returns `pressure.clamp(0, 1) ^ gamma` as a [double].
double applyPressureCurve(double pressure, double gamma) =>
    pow(pressure.clamp(0.0, 1.0), gamma).toDouble();

/// Manages [PenConfig] persistence and live updates.
///
/// Load with [PenConfigController.load], then listen to changes via
/// [ChangeNotifier]. Setters immediately update the in-memory value,
/// notify listeners, and persist to SharedPreferences.
class PenConfigController extends ChangeNotifier {
  PenConfigController._(this._prefs, this._value);

  /// The SharedPreferences key under which [PenConfig] JSON is stored.
  static const prefsKey = 'pen_config_v1';

  final SharedPreferences _prefs;
  PenConfig _value;

  /// The current pen configuration.
  PenConfig get value => _value;

  /// Loads persisted config from SharedPreferences. Falls back to defaults
  /// if no config has been saved yet or if the stored JSON is invalid.
  static Future<PenConfigController> load() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(prefsKey);
    PenConfig config;
    if (raw == null) {
      config = const PenConfig();
    } else {
      try {
        config = PenConfig.fromJson(
          jsonDecode(raw) as Map<String, dynamic>,
        );
      } catch (_) {
        config = const PenConfig();
      }
    }
    return PenConfigController._(prefs, config);
  }

  Future<void> _persist() async {
    await _prefs.setString(prefsKey, jsonEncode(_value.toJson()));
  }

  Future<void> setSideButton(PenButtonAction action) async {
    _value = _value.copyWith(sideButton: action);
    notifyListeners();
    await _persist();
  }

  Future<void> setEraserEnd(PenButtonAction action) async {
    _value = _value.copyWith(eraserEnd: action);
    notifyListeners();
    await _persist();
  }

  /// Sets [PenConfig.pressureGamma]. Clamped to [0.3, 3.0].
  Future<void> setPressureGamma(double gamma) async {
    _value = _value.copyWith(pressureGamma: gamma.clamp(0.3, 3.0));
    notifyListeners();
    await _persist();
  }

  /// Sets [PenConfig.palmRejectionMs]. Clamped to [0, 500].
  Future<void> setPalmRejectionMs(double ms) async {
    _value = _value.copyWith(palmRejectionMs: ms.clamp(0.0, 500.0));
    notifyListeners();
    await _persist();
  }

  Future<void> setFingerDrawing(bool enabled) async {
    _value = _value.copyWith(fingerDrawing: enabled);
    notifyListeners();
    await _persist();
  }

  Future<void> setPenWidth(double width) async {
    _value = _value.copyWith(penWidth: width);
    notifyListeners();
    await _persist();
  }

  Future<void> setHighlighterWidth(double width) async {
    _value = _value.copyWith(highlighterWidth: width);
    notifyListeners();
    await _persist();
  }

  /// Sets [PenConfig.pressureSensitivity]. Clamped to [0, 1].
  Future<void> setPressureSensitivity(double sensitivity) async {
    _value = _value.copyWith(pressureSensitivity: sensitivity.clamp(0.0, 1.0));
    notifyListeners();
    await _persist();
  }
}